Method of heat exchange



1934. H. s. COLBY ET AL 1,970,534

METHOD OF HEAT EXCHANGE Original Filed Jan. 2, 1930 2 Sheets-Sheet 1INVENTORS #M m 4.44

1934- H. s. COLBY ET AL METHOD OF HEAT EXCHANGE Original Filed Jan.2.1930 2 Sheets-Sheet 2 IlIllflI/lllll Patented Aug. 14,, 1934 PATENTOFFICE mz'rnon or near axcmoa Haldwell s. 0015i and Per Hilmer Karlsson,

Wellsville, N. Y., aasignors to Air Preheater Corporation, a corporationof New York Original application January 2, 1930, Serial No. 418,029.Divided and this application July 30,

1932, Serial No. 626,772

8 Claims. (01. 257-6) This application is a division of applicationSerial No. 418,029, filed January 2, 1930, for Heat exchangeinstallations.

Our present invention relates to the operation of heat exchanginginstallations, and has particular reference to heat exchange systems forhot gases containing excessive amounts of solid impurities.

One object of the invention is to provide a novel method of utilizing aheat exchanger and gas purifier for purifying impurity laden gases ofthis character while conserving their heat content.

Another object is to improve the operation of a heat exchanger byutilizing novel scavenging means.

These and other'objects and advantageous features will be readilyapparent from the detailed description following, in Conjunction withthe accompanying drawings, and will be particularly pointed out in theappended claims.

In the drawings:

Fig. 1 is a diagrammatic view of a specific form of installationsuitable foruse with blast furnace gases;

Fig. 2 is a perspective view, partly broken away, of the improved heatexchanger;

Fig. 3 is a horizontal section through the upper portion of the heatexchanger, showing the scavenging and sealing air passages; and

Fig. 4 is a. detail vertical section on the line 44 of Figure 3.

The utilization of blast furnace gases for steam generation involves theproblem of removing dust and other solid impurities from the hot gases.These hot gases contain a. tremendous quantity of fine dust which iscarried in suspension, and have required washing befor passage to theboilers in order to prevent deposit of dust and clogging of the pipelines, gas furnace, and boiler units. The washing process reduces'theamount of dust to a small quantity, in the neighborhood of 1% of theoriginal amount, but the washed gases retain moisture which isafterwards liberated during combustion of the gases in the boiler, thismoisture being sufiicient to produce clogging of the pipe lines betweenthe washer and the point of consumption as well as in the burnerequipment of boilers under which the gases are burned, by depositingsludge therein.

We have found that passing the washed gas through'a preheater raises thetemperature sufficiently so that the gas will carry all the water,

in vapor form, the temperature obtained being sufilciently high toprevent precipitation or liberation of moisture in. the ducts orconduits and in the burner equipment; and we have devised a noveloperating procedure for a heat exchanger and gas washer to minimize thesludge deposit, the' hot gases being passed through an air preheater toreduce their temperature, then to the washer, and then back into the airpreheater to reabsorb the heat initially transferred. We have also anovel scavenging operation to eliminate transfer of dust or dirty gasesto thewashed gases passing to the boiler; and the following is adetailed description of one specific arrangement to which the novelprinciples of our invention may be applied.

Referring to the drawings, hot gases from the blast furnace 10 passthrough the conduit 11 into the hot gas side of a preheater 12,preferably of the rotary regenerative type. The cooled gases then passthrough the conduit 13 into a gas washer 14 of any well-known type, andthe washed purified gases arereturned into the heat exchanger 12 througha conduit l5, and are then led through conduit 16 to th boiler plant1'7.

The heat exchanger is shown in detail in Figures 2, 3, and 4, andincludes an outer casing 18, and a rotor 19 rotatably mounted thereinand divided into radial sectors 20 each containing regenerative material21. The casing is divided into a hot gas section and a washed gassection by a transverse partition 22, and two radial partitions 23, 24.,the said partitions defining two radial sectors corresponding in size tothe sectors 20 of the rotor 19. The sector between the partitions 22 and24 is sub-divided by an additional partition-25 into a scavenging sector26 and a gas sealing sector 27. e

A hot gas inlet 28 and outlet 29 permit the hot gases to traverse thehot gas section of the preheater as the regenerative material intherotor sectors 20 passes to absorb and store heat therefrom, and a washedgas inlet 30 and outlet 31 permit the washed gases to pass through theheated regenerative material to extract the stored heat.

The partitions 32 separating the sectors 20 have sealing strips 33 atboth the upper and the lower ends thereof, contacting with a closuremember 34 which is in alignment with and of the same size as the sectorbetween partitions 22 and 24. The lower sector member 34 has a port35therein leading to the atmosphere or to plies compressed washed gas athigh pressure to sector 26 through pipe line 3'land compressed washedgas at a lower pressure to sector 2'7 through pipe line 38, the pressureof the gas supplied to sector 27 being greater than the pressure of thehot gases which pass through the hot gas portion of the heat exchanger.As shown in Figs. 1 and 4, the lower pressure washed gas is supplied tothe sealing sector on both sides thereof, in order to maintain thesealing pressure. Such leakage as occurs is to the washed gaspassageway, thus conserving the washed gas.

The high pressure washed gas preferably passed out through the port 35to the conduit 13 to join the hot 'gases for washing and cleaning in thegas washer l4.

The rotor 19 has an annular flange 39 on which an annular gear 40 ismounted, in oper ative engagement with a pinion (not shown) rotatedthrough operating mechanism 41. The flange 39 is supported on aplurality of spaced rollers 42 suitably mounted in the casing 18, andcarries spaced projections 45, preferably formed by bolt heads or thelike inserted in the flange, which projections ride on the rollers 42and thus cause a jarring or a jolt'ng of the rotor to dislodge collecteddust.

The hot gases from a blast furnace or furnaces have a temperature in theneighborhood of 300 degrees Fahrenheit; this temperature is reduced inpassing through the heat exchanger to about 200 degrees F., the washercausing-a further temperature drop to about 65 degrees F.; the lowertemperature of the gases entering the washer thus reduces the work ofthe washer and decreases the percentage of absorbed moisture. The washedgases now pass through the heat exchanger, with a resulting temperatureincrease to about 150 degrees F., thus conserving a large part of thegas heat and at the same time reducing the moisture content. As therotor turns, the high pressure scavenging washed gas blows through theregenerative material, removing the dust and dust-laden hot gasestherefrom, the constant jarring of the rotor preventing the formation ofhard deposits; in addition, the maintenance of a higher pressure betweenpartitions 22 and 24 and above the separating sector member 34 preventsleakage of hot gases across into the washed gas section. If desirableor'necessary, a similar higher pressure arrangement may be provided forthe separating sector between partitions 22 and 23.

While we have described a preferred method of the utilization of ourinvention, desired changes in operating procedure may be made to meetthe needs of particular installations, within the scope of the inventionas defined in the appended claims.

1. In a process for purifying hot gases containing solid impurities, thesteps of transferring heat from the hot gases .to a regenerative mass tolower the gas temperature, washing the cooled gases, retransferring theheat from said regenerative mass to the washed cooled gases to reheatthe same. and scavenging said regenerative mass after the retransfer ofheat.

2. In a method of heat exchange, the steps of conducting hot and coldfluidsthrough heat exchange apparatus in adjacent streams, andmaintaining a fluid pressure between said streams at least equal to thepressure of the hot fluid.

3. In a method of heat exchange, the steps of conducting hot and coldfluids through regenerative material in adjacent streams, andmaintaining a fluid pressure between said streams at least equal to thepressure of the hot fluid.

4. In a method of heat exchange, the steps of conducting hot and coldfluids through heat exchange apparatus in adjacent streams, said hotfluids containing impurities and said cold fluids being relativelyclean, and interposing a curtain of clean fluid between said hot andcold fluids to prevent admixture thereof.

5. In a method of heat exchange, the steps of conducting hot and coldfluids through regenerative material in'adjacent streams, said hotfluids containing impurities and said cold fluids being relativelyclean, and interposing a curtain of clean fluid between said hot andcold fluids to prevent admixture thereof.

6. In a method of heat exchange, the steps of passing hot fluid througha heat exchanger to cool the same, cleaning said cooled fluid, passingthe cleaned cooled fluid through the heat exchanger to heat the same,said hot fluid and said cleaned cooled fluid passing through saidregenerative material simultaneously, and utilizing part of the cleanedcooled fluid under pressure as a fluid curtain to prevent admixture ofsaid hot fluid and said cleaned cooled fluid during their flow throughthe heat exchanger.

7. In a method of heat exchange, the steps of passing hot fluid throughregenerative material to cool the same, cleaning said cooled fluid,passing the cleaned cooled fluid through the regenerative material toheat the same, said hot fluid and said cleaned cooled fluid passingthrough said regenerative material simultaneously, and utilizing part ofthe cleaned cooled fluid under pressure as a fluid curtain to preventadmixture of said hot fluid and said cleaned cooled fluid during theirflow through the regenerative material.

8. In a method of heat exchange, the steps of passing hot fluid throughregenerative material to cool the fluid, cleaning the cooled fluid,scavenging the regenerative material, and passing the cleaned cooledfluid back through the regenerative material to reheat the fluid, saidscavenging being prior to the passing of the cleaned cooled fluid backthrough the regenerative material.

HALDWELL S. COLBY. P. HILMER KARLSSON.

